October 26, 2015

Temperature and its effects on food consumption in the Siberian Husky

Exploring metabolic mechanisms and trends through various climates

In the first half of the 20th century, biologists believed that canine metabolic rates did not vary by season or climate.  Though many arctic dogs require increased insulation in the winter, it was thought that the seasonal alteration in the thermal capability of fur compensated enough for this change.  The authors of this study sought to test, and perhaps disprove, this hypothesis that metabolism is a constant regardless of temperature. 

In order to measure canine metabolism, 2 groups of dogs were procured: well-insulated Husky dogs raised in Alaska, and poorly insulated beagles raised in the warmer climate of San Francisco.  The observations of these animals lasted a full year; the study began in November of 1960 and finished in November of 1961.  During that year, all of the subjects lived outside, regardless of climate.  The temperature ranged from -14C in January to 17C in July.  Their only protection from the elements was a small plywood shelter.  In order to measure metabolism over time, the researchers recorded the amount of food each dog ate every day.  The dogs were fed balanced meals and given ample water.  by measuring the amount of food provided and subtracting the amount of food remaining at the end of a meal, the total amount of calories consumed could be determined for each group. 

The experiment continued without obstacle for the entire year.  After the study ended, the data could be analyzed, and correlations drawn between calorie consumption and temperature.  It was this connection that scientists believe would prove or disprove the hypothesis of constant metabolism.  In the case of the five huskies, there existed a very strong correlation (r=-0.821) between food consumption and ambient temperature.  Caloric intake was a surprising 60% greater in the winter months than in the summer (80kcal/kg/day vs. 49kcal/kg/day).  Though there was no simple relationship between daily temperature and the amount of food eaten, the trend throughout the seasons was apparent: the huskies’ consumption increased greatly in the colder weather, so as to provide the subjects with more insulation against the elements. 

Though the caloric intake was the greatest in the winter, the body weight of the subjects was the lowest during this time period.  It can be drawn from this relationship that the metabolism of the huskies was at its peak in the winter months, burning all of the extra food to provide warmth and insulation in the below freezing weather.  A similar pattern was noticed in the beagle group, showing that previous individual or breed tolerance of the cold climate had little to no effect on the metabolic rates of the subjects. 

The variance in correlation can be partially attributed to the fact that the appetites of the animals lagged behind their caloric requirements.  Thus, they were eating too much into the summer and too little in the winter to maintain constant body weight.  The Huskies also exhibited a noticeable increase in hair growth during the months of November and December.  For the most part though, this study proved that nutrition, not natural and seasonal bodily adaptations, accounts for the majority of the insulation and tolerance to cold weather in the Husky.

 

John L. Durrer and John P. Hannon

1962

Seasonal variations in caloric intake of dogs living in an arctic environment

American Journal of Physiology 202: 375-8

http://ajplegacy.physiology.org/content/ajplegacy/202/2/375.full.pdf

Full article here

Article by Grant Black